A great place to learn keyboard shortcuts is from the drop-down menus. As you make a selection, make note of the keyboard shortcut listed next to it, if any. Certain things will jump out at you, like ⌘N for New or ⌘P for Print.

Be careful - the keyboard shortcuts apply to the application named in the menu bar.

    For the most part, you can substitute the ⌘ key for the PC Ctrl key. Most shortcuts you already know will work this way:

            ⌘O :    open a file

            ⌘C :    copy

            ⌘X :    cut

            ⌘V :    paste

            ⌘S :    save

      ⌘⇧S :     save as

            ⌘Z :    undo

            ⌘B :    bold type

            ⌘U :    underlined type

            ⌘I :      italics

           ⌘⇥:     switch between open applications

   

Quit

    Probably the most useful is ⌘Q to quit the application. The reason it is so useful is, as you may already know, when you close an application window by clicking the red stoplight, the application keeps running in the background so you can restart it quickly (you know an application is still running because it has a dot underneath its dock icon).

Force Quit

    In Windows, to access the Task Manager and end a process you hit Ctrl-Alt-Del. In Mac OS hit ⌘⌥⎋ to bring up the Force Quit Applications window. You can also force quit an application by ⌥right-clicking (holding the option key while right-clicking) the application’s dock icon (but should only be done if the application is not responding).  

Send Items Straight to the Trash

    ⌘⌫ sends the selected item straight to the trash, without the warning from Mac OS.

Quickly Rename a File or Folder

    When you select a file or folder and hit ENTER, it does not open. Instead, you are prompted to rename it. To open a selected file or folder with the keyboard, select it and hit ⌘O.

App Switching

    You can use ⌘⇥ to switch between open applications, but to switch between open windows of a single application press ⌘TILDE (~).

Hiding & Minimizing

    ⌘H hides the front-most application, while ⌘M minimizes it to the right side of the dock. The difference is, if you hide an application, you can still switch back to it with ⌘⇥. If you minimize it, you have to click on it’s minimized icon in the dock to resume work/play.

Sleep & Shut Down

⌘⌥⏏ will immediately put your computer to sleep.

⌃⌘⌥⏏ will immediately shut down your computer.

⌃⏏ brings up a shut down menu.

⌃⌘⏏ quits all applications and restarts.

⌘⇧Q will log out the current user

Apple’s Keyboard Shortcuts page is pretty helpful for more info.